Lone Atrial Fibrillation

"Lone" or idiopathic AF (29), occurs in a small percentage (5-20%) of all patients with AF. As the term implies, this entity corresponds to AF in the absence of any clinical entity associated with the disease, and is therefore a diagnosis of exclusion. Excluded from this category are patients with structural heart disease, including hypertension alone, or with noncardiac diseases that have been associated with AF (see Table 1); this diagnosis is usually reserved for patients less than 65 yr of age. Patients with "lone" AF are therefore more likely to be younger and to present with paroxysmal or persistent, rather than permanent, episodes of AF. While the mechanism remains unclear, some authors have suggested that a subset of these patients may have a familial predisposition (30,31), and other reports imply atrial myocarditis as a possible cause (32), but these underlying associations are likely not to be causal in the vast majority of patients with "lone" AF. The mode in which initiation occurs in patients with lone AF may shed some light on the underlying mechanism and provide a guide for future therapeutic intervention. Modulation of the autonomic system, for example, is often

Table 1

Conditions Associated with Atrial Fibrillation

Non-Cardiac Disease

Endocrine Disease

Cardiac Disease

Primary Atrial Disease Fibrosis

Myocardial degeneration with aging Atrial Scar post myocarditis Atrial infarction Post atriotomy scar Infiltrative/Inflammatory Disease Sarcoidosis Hemochromatosis Amyloidosis

Acute pericarditis or myocarditis Valvular Heart Disease

Mitral Stenosis/Regurgitation Aortic Stenosis/Regurgitation Congenital Heart Disease Cardiomyopathy Dilated Hypertrophic Infiltrative Ischemic Acute Coronary syndromes Ventricular MI Acute ventricular ischemia Hypertension

Post Coronary Artery Bypass Graft Surgery

Hyperthyroidism Diabetes Mellitus Pheochromocytoma

Pulmonary Disease

Chronic Obstructive Lung Disease Pulmonary Hypertension Pulmonary Embolism Neoplasm High Adrenergic Tone

Post non-cardiothoracic surgery Systemic infection Electrolyte abnormalities Other Familial

High Vagal Tone implicated as the possible precipitant of AF in subsets of this patient population. Some patients, such as young males and athletes, show a tendency to develop paroxysms of lone AF when vagal tone is enhanced (33) (at night, or post-prandially), while other patients, usually older, seem to develop AF in the face of adrenergic stimulation. Finally, the patients with lone AF should be carefully screened for other atrial arrhythmias, which may be the precursors to AF. If arrhythmias such as atrial flutter, AV reciprocating tachycardia, AV nodal reentrant tachycardia (AVNRT) and atrial tachycardia are recognized as the precipitants of AF, curing these may also eliminate AF. It is of particular interest that even unifocal premature atrial beats may be the target of ablative therapy to cure lone AF in a subset of patients with this disease (34).

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